Stabilizing single atom contacts by molecular bridge formation

TL;DR

This paper investigates how dithiol molecules form bridges in gold junctions, stabilizing atomic gold contacts, and proposes a model explaining the mechanical role of these molecules in the process.

Contribution

It introduces a hypothesis that alkanedithiol molecules pre-bridge gold electrodes, stabilizing atomic contacts, supported by a spring model analysis.

Findings

Alkanedithiol molecules form pre-bridges before gold atomic junctions break.

Molecular bridging stabilizes the gold-gold contact during junction formation.

A spring model explains the stabilization mechanism.

Abstract

Gold-molecule-gold junctions can be formed by carefully breaking a gold wire in a solution containing dithiolated molecules. Surprisingly, there is little understanding on the mechanical details of the bridge formation process and specifically on the role that the dithiol molecules play themselves. We propose that alkanedithiol molecules have already formed bridges between the gold electrodes before the atomic gold-gold junction is broken. This leads to stabilization of the single atomic gold junction, as observed experimentally. Our data can be understood within a simple spring model.